Mozilla Developer NetworkIntroduced in Gecko 2.0
(Firefox 4 / Thunderbird 3.3 / SeaMonkey 2.1)JavaScript 1.8.5 is the version of JavaScript included in Firefox 4.
New functions
| Function | Description |
|---|---|
Object.create |
Creates a new object with the specified prototype object and properties. bug 492840 |
Object.defineProperty |
Adds the named property described by a given descriptor to an object. |
Object.defineProperties |
Adds the named properties described by the given descriptors to an object. |
Object.getOwnPropertyDescriptor |
Returns a property descriptor for a named property on an object. bug 505587 |
Object.keys |
Returns an array of all enumerable properties on an object. bug 307791 |
Object.getOwnPropertyNames |
Returns an array of all enumerable and non-enumerable properties on an object. bug 518663 |
Object.preventExtensions |
Prevents any extensions of an object. bug 492849 |
Object.isExtensible |
Determine if extending of an object is allowed. bug 492849 |
Object.seal |
Prevents other code from deleting properties of an object. bug 492845 |
Object.isSealed |
Determine if an object is sealed. bug 492845 |
Object.freeze |
Freezes an object: other code can't delete or change any properties. bug 492844 |
Object.isFrozen |
Determine if an object was frozen. bug 492844 |
Array.isArray |
Checks if a variable is an array. bug 510537 |
Date.toJSON |
Returns a JSON format string for a Date object. |
Function.prototype.bind |
Creates a new function that, when called, itself calls this function in the context provided (with a given sequence of arguments) bug 429507 |
New ECMAScript5 features
getandsetoperators now allows the identifier to be numeric or a string. bug 520696Function.apply()can accept any array-like object as the arguments list, instead of only true arrays.- strict mode support
Array.toString()now works even on non-arrays by either returning the result of calling itsjoin()method if one is available or by calling itstoString()method.
Other standardization work
Various non-standard syntaxes for defining getters and setters have been removed; ECMAScript 5 defined syntax has not been changed. These were all pretty esoteric and rarely used; if this affects you, see this blog post for details.
New objects
| Object | Description |
|---|---|
Proxy |
Offers support for creating Object and Function proxies that enable meta-programming in JavaScript. |
Changes to global objects
- ISO 8601 support in
Date - The
Dateobject'sparse()method now supports simple ISO 8601 format date strings. - Global objects made read only
- The
NaN,Infinity, andundefinedglobal objects have been made read only, per the ECMAScript 5 specification.
Additional changes
obj.__parent__andobj.__count__become obsolete. Some information about why: SpiderMonkey change du jour: the special __parent__ property has been removed bug 551529 & bug 552560.- Trailing commas no longer accepted in
JSON.parse().
JavaScript (SpiderMonkey) API changes
Note: Locale callbacks (as specified in the JSLocaleCallbacks structure) should not free the memory buffer passed to them; this buffer is managed by the SpiderMonkey runtime.
The JS_NewString() function was removed in SpiderMonkey 1.8.5. Use JS_NewStringCopyN() instead.